In an island nation of just 300,000 people, sleeping with distant relatives may be inevitable. Sleeping with close relatives, however, remains something most would prefer to avoid. Now there’s an app for that.

The News of Iceland reports that a team of software engineers has scraped a publicly accessible genealogy website called Íslendingabók—the Book of Icelanders—to produce an Android app called ÍslendigaApp. Along with a range of more conventional search functions, the app features a “bump” function that lets two users tap phones to see how closely they are related. Too close a match, and an “incest alarm” will sound. The pitch: “Bump the app before you bump in bed.”

So far it’s drawing rave reviews, with a 4.5 out of 5 rating on the Google Play store. One user who commented on the app’s website only regretted that it wasn’t released a little earlier: “If I would have had this app last year,” he wrote, “I probably wouldn’t have gone home with my cousin.”